Design Of Low-profile Wideband Dual-polarized Antennas

As the development of the wireless communication systems,to cover multi bands,the requirements for wideband antennas increase.Meanwhile,due to the limited space for communication equipment,miniaturized designs attract a lot of attentions.Therefore,the researches on the wideband antennas with low profiles are significant.Dual-polarized antennas are widely used for the suppression of multipath fading and the improvement of channel capacity.However,in the existing designs of the dual-polarized antennas,it is found that the wide bandwidth coverage and its low-profile performance have mutual restrictions,which cannot meet the low-profile wideband application scenarios.To solve this problem,a low-profile wideband dual-polarized antenna and a dual-band dual-polarized antenna are designed in this thesis.The specific content includes the following two parts:1.A low-profile wideband dual-polarized antenna is proposed.The antenna is based on the principle of multi-mode patches,combined with the differential symmetrical structure of the dipoles.Firstly,the arrow-shaped patch is designed to excite three modes simultaneously,contributing to the wide bandwidth.Secondly,to obtain stable radiations in the operating bands,shorting pins are introduced on the two wings of the arrow-shaped patch.Finally,the coplanar coupling feed is adopted to achieve impedance matching in the broad bandwidth.To verify the above design,the dual-polarized antenna is fabricated and measured.The proposed dual-polarized antenna operates in 2.10 GHz-3.95 GHz,possessing a 10-dB impedance bandwidth of 61%,a profile of 0.1λ₀,an average gain of 7.31 dBi,and an isolation of 25 dB.Compared with other dual-polarized antennas,the antenna achieves a broader bandwidth with a low profile.The results have been submitted to IEEE Transactions on Antennas and Propagation.2.A dual-band wideband low-profile dual-polarized antenna is proposed.The antenna is also based on the multi-mode patch combined with the differential symmetrical structure of the dipoles.Firstly,four modes can be excited simultaneously by chamfering the rectangular patch and adjusting its aspect ratio.The first two modes form the lower passband.To stabilize the gain of the lower passband,a pair of long slots are introduced to move the TM₀₂ mode out of the lower band.As the higher passband,another pair of short slots are etched beside the feeding probe and the mode of the slot is excited,which works with TM₁₂ mode together to generate the higher passband.Finally,the profile of the proposed antenna is only 0.096λ_0L.For the lower passband,the proposed antenna operates from 2.53 GHz to 2.93 GHz,with a14.6%10-dB impedance bandwidth,and an average gain of 8.16 dBi.For the higher passband,it operates from 4.5 GHz to 5.36 GHz,with a 17.4%bandwidth,and an average gain of 6.03dBi.The isolations of both bands are more than 23 dB.